The invention relates to devices and methods for determining barrier properties of coatings, and more particularly, to combinatorial barrier property screening devices and methods.
Coatings having barrier properties are used for many packaging and protective applications. The coatings, as barriers, typically separate a system, such as an electronic component, a part of an engineering structure or an article of food, from an environment. As such, the barrier properties of the coating define the permeability or resistance of the particular coating to a given material of interest. For example, typical barrier properties include the resistance of a coating to oxygen or to moisture.
In an effort to discover new and improved coating formulations, the analysis of new coatings is limited by the large sample sizes and long exposure time periods typically required for screening each new coating formulation. The large sample size and long exposure times to one or more materials of interest to test a coating formulation are generally required in order to detect the transport of the material of interest through the coating. Because the barrier properties of a coating may be high, only small amounts of the material of interest may penetrate the coating and/or it may take a long time for such penetration.
For example, the transport of oxygen through a coating is typically measured by exposing one side of the coating to oxygen, while nitrogen gas sweeps the other side of the coating to an oxygen detector. The detector measures the rate that oxygen comes through the coating. In order for the detector to receive a measurable amount of oxygen, a large sample size is utilized. Same approach is utilized for measurements of moisture permeability of coatings, where a water vapor detector used instead. Besides the disadvantage of requiring a large surface area, another problem with this technique is the difficulty of mapping oxygen or/and water vapor transport of different spatial regions of the single coating or performing evaluation of multiple coatings with the same detection system simultaneously.
Another disadvantage of typical barrier coating measurement techniques is that the edges of the coating typically mischaracterize the measurement results if the cross section of the analyzed barrier coating is small. This xe2x80x9cedge effectxe2x80x9d provides another factor to account for in measuring and analyzing new coating formulations, thereby reducing the efficiency of the process.
Thus, there remains an unmet need to provide devices and methods for efficiently measuring the barrier properties of a coating or combination of coatings. There remains a further need to provide devices and methods such that measurement errors associated with coating edge effects are reduced or eliminated.
The present invention discloses methods and devices for measuring barrier properties of coating arrays.
In one embodiment, a device for measurement of barrier properties of barrier coatings includes a waveguide having an external surface with a chemically sensitive layer disposed about the external surface of the waveguide, where the chemically sensitive layer is responsive to a material of interest. A predefined number of barrier coatings are deposited onto the chemically sensitive layer, and each of the barrier coatings has a corresponding barrier property with respect to the material of interest. A light source is operable to propagate a wave within the waveguide, and a detector is operable to measure impacts associated with the propagated wave and associated with the respective barrier property of each of the plurality of barrier coatings. A correlator correlates the measured impact with a value of the barrier property for each of the plurality of barrier coatings.
In another embodiment, a method for measuring barrier properties of coating arrays includes applying a chemically sensitive layer to an exterior surface of a waveguide, where the chemically sensitive layer has at least one characteristic that changes in response to exposure to a material of interest. Also, the method includes applying an array of barrier coatings to the chemically sensitive layer, where each coating of the array of barrier coatings has a barrier property with respect to the material of interest. A wave is transmitted through the waveguide and the waveguide with the applied array of barrier coatings is exposed to the material of interest. The impact associated with the propagated wave is detected and correlated with a value of a barrier property for each of the array of barrier coatings.
Additional advantages and novel features of the invention will be set forth in part in the description that follows, and in part will become more apparent to those skilled in the art upon examination of the following or upon learning by practice of the invention.